Orc system and process for generation of energy by organic rankine cycle

Abstract

An ORC system for generation of energy by Organic Rankine Cycle comprises a turbo-expander ( 40 ) of a radial centrifugal type formed by a single rotor disc ( 108 ) and provided with an auxiliary opening ( 40 c ). The auxiliary opening ( 40 c ) is interposed between an inlet ( 40 a ) and an outlet ( 40 b ) of the turbine ( 40 ) and is in fluid connection with an auxiliary circuit ( 1000, 2000 ), such as to extract from the turbo-expander ( 40 ) or inject into the turbo-expander ( 40 ) the organic working fluid at an intermediate pressure between an injection pressure and a discharge pressure.

The invention claimed is: 
     
       1. ORC system for generation of energy by Organic Rankine Cycle having two or more pressure levels, comprising:
 at least one heat exchanger to exchange heat between a high temperature source and an organic working fluid, to heat, evaporate and superheat said organic working fluid; 
 at least one turbo-expander presenting an inlet in use fed with the vaporized organic working fluid coming out from the heat exchanger, to make a conversion of the thermal energy present in the organic working fluid into mechanical energy according to a Rankine cycle; 
 at least one condenser where in use the vaporized organic working fluid coming out from an outlet of said at least one turbo-expander is condensed; 
 at least one pump to feed the organic working fluid coming out from the condenser to said at least one heat exchanger; 
 at least an auxiliary circuit for injection of the organic working fluid into said turbo-expander; 
 wherein said at least one turbo-expander is of radial centrifugal type and comprises: 
 a single rotor disc carrying a plurality of rotor blades; 
 at least an auxiliary opening interposed between the inlet and the outlet and in fluid communication with said auxiliary circuit, to extract or inject the organic working fluid at an intermediate pressure between an inlet pressure and an outlet pressure; wherein the turbo-expander comprises a plurality of stages radially disposed one after the other and wherein the auxiliary opening opens between two of said stages; wherein the radial distance between the two stages between which the auxiliary opening opens is greater than the radial distance between the other stages to delimit an injection chamber of the organic working fluid. 
 
     
     
       2. The system according to  claim 1 , wherein the radial distance between the two stages between which the auxiliary opening opens is about ten times greater than the radial distance between the other stages. 
     
     
       3. The system according to  claim 1 , wherein the auxiliary opening opens upstream of most radially peripheral stage. 
     
     
       4. The system according to  claim 1 , wherein the single rotor disc is cantilevered. 
     
     
       5. The system according to  claim 1 , wherein the turbo-expander comprises a static casing, wherein the single rotor disc is housed into the casing wherein the casing is cantilevered too. 
     
     
       6. The system according to  claim 5 , wherein the auxiliary opening is made in a front wall of the casing. 
     
     
       7. The system according to  claim 1 , wherein the circuit for injection of working fluid into the turbo-expander comprises a vaporizer; wherein, in use in the vaporizer, part of the organic working fluid coming out from the condenser exchanges heat with a high temperature source before said part of the organic working fluid coming out from the condenser is re-introduced into the turbo-expander through the auxiliary opening. 
     
     
       8. The system according to  claim 1 , further comprising a recuperator, wherein the inlet circuit comprises a connecting branch provided with a vaporizer which connects a point located downstream of the pump and the recuperator and upstream of the heat exchanger with the auxiliary opening into the turbo-expander. 
     
     
       9. An ORC process for energy production by an Organic Rankine Cycle, comprising:
 exchanging heat in at least a heat exchanger, between a high-temperature source and an organic working fluid, such as to heat, evaporate and super-heat the organic working fluid; 
 supplying the organic working fluid in a vaporized stage in outlet from the heat exchanger through an inlet opening of at least a turbo-expander, to realize a conversion of heat energy present in the organic working fluid into mechanical energy according to a Rankine cycle; 
 condensing, in at least a condenser, the organic working fluid in the vaporized stage from an outlet opening of the at least a turbo-expander; 
 supplying, via at least a pump, the organic working fluid coming from the condenser towards the at least a heat exchanger; 
 wherein the process further includes injecting the organic working fluid into the turbo-expander via at least an auxiliary circuit; 
 wherein the at least a turbo-expander is a radial centrifugal type and comprises: one only rotary disc bearing a plurality of rotor blades; at least an auxiliary opening interposed between the injection opening and the discharge opening and in fluid connection with the auxiliary circuit; 
 wherein the organic working fluid is injected into the at least an auxiliary opening at an intermediate pressure between an inlet pressure and a discharge pressure; 
 wherein the radial distance between the two stages between which the auxiliary opening opens is greater than the radial distance between the other stages to delimit an injection chamber of the organic working fluid. 
 
     
     
       10. The process according to  claim 9 , wherein the working fluid flow enters the turbo-expander along an axial direction in a radially more internal zone of the turbo-expander and exits, expanded, along a radial or axial direction in a radially more external zone of the turbo-expander. 
     
     
       11. ORC system for generation of energy by Organic Rankine Cycle having two or more pressure levels, comprising:
 at least one heat exchanger to exchange heat between a high temperature source and an organic working fluid, to heat, evaporate and superheat said organic working fluid; 
 at least one turbo-expander presenting an inlet in use fed with the vaporized organic working fluid coming out from the heat exchanger, to make a conversion of the thermal energy present in the organic working fluid into mechanical energy according to a Rankine cycle; 
 at least one condenser where in use the vaporized organic working fluid coming out from an outlet of said at least one turbo-expander is condensed; 
 at least one pump to feed the organic working fluid coming out from the condenser to said at least one heat exchanger; 
 at least an auxiliary circuit for injection of the organic working fluid into said turbo-expander; 
 wherein said at least one turbo-expander is of radial centrifugal type and comprises: 
 a rotor disc carrying a plurality of rotor blades; 
 at least an auxiliary opening interposed between the inlet and the outlet and in fluid communication with said auxiliary circuit, to inject the organic working fluid at an intermediate pressure between an inlet pressure and an outlet pressure; wherein the turbo-expander comprises a plurality of stages disposed one after the other and wherein the auxiliary opening opens between two of said stages; wherein the distance between the two stages between which the auxiliary opening opens is greater than the distance between the other stages to delimit an injection chamber of the organic working fluid.